Abstract 49: Prolyl Isomerase Pin1 Regulates Cardiac Hypertrophy via Controlling Phosphorylation of Akt and MEK
Rationale: Kinases and phosphatases regulate crucial aspects of growth and survival through phosphorylation and dephosphorylation of target substrates. Processes of cardiac hypertrophy, myocardial infarction, and heart failure are dictated in part by which kinases or phosphatases are involved and also by the intensity and duration of specific enzymatic activities. While research has identified numerous critical regulatory kinases and phosphatases in the myocardium, the intracellular mechanism for temporal regulation of signaling duration and intensity remains obscure. In the non-myocyte context, control of folding, activity, stability, and subcellular localization of proteins responsible for growth and survival is mediated by the prolyl isomerase Pin1.
Objective: To establish the role of Pin1 in the heart.
Method and Results: Initial characterization of myocardial Pin1 involved assessment of expression and localization during postnatal development or pathological challenge. Pin1 protein level was decreased and the location of Pin1 was changed from nucleus to cytoplasm with increasing age. Next, Pin1 protein expression and localization were assessed in the pathological challenged heart. Pin1 protein expression increases with pressure overload and ischemia, particularly in perivascular areas and in border zone myocytes, respectively. To determine the role of Pin1 on cardiac hypertrophy, siRNA to Pin1 (siPin1) was applied to neonatal rat cardiomyocytes. Western blot analysis showed that siPin1 decreased phosphorylation of Akt, and immunohistochemical analysis showed that siPin1 reduced cardiomyocyte size in response to high serum. siPin1 also decreased phosphorylation of MEK and reduced cardiomyocyte size in response to phenylephrine treatment. Furthermore, cardiac hypertrophy induced by transaortic constriction was ameliorated in Pin1 knockout mice, compared with littermate wild type mice.
Conclusion: Expression and location of Pin1 during development and in response to pathologic challenge point to an important role for Pin1 in adaptation to myocardial growth or stress. Collective evidence indicates that Pin1 controls cardiac hypertrophy at least in part via regulating phosphorylation of Akt and MEK.
- © 2012 by American Heart Association, Inc.